X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTarget%2FR600%2FSIFixSGPRCopies.cpp;h=086b44433c2ebf04096e3d4a50a8fe4d0d48cbb8;hp=a9a7c5ce0fe6a6c285b1295c194bb4d9535136b7;hb=a3837424391e08fe88bf5d65ea265464d11c1528;hpb=c279ae979e7b60c244ad2b5e61ba93eab08ade3b

diff --git a/lib/Target/R600/SIFixSGPRCopies.cpp b/lib/Target/R600/SIFixSGPRCopies.cpp
index a9a7c5ce0fe..086b44433c2 100644
--- a/lib/Target/R600/SIFixSGPRCopies.cpp
+++ b/lib/Target/R600/SIFixSGPRCopies.cpp
@@ -66,6 +66,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "AMDGPU.h"
+#include "AMDGPUSubtarget.h"
 #include "SIInstrInfo.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -185,7 +186,8 @@ bool SIFixSGPRCopies::isVGPRToSGPRCopy(const MachineInstr &Copy,
   const TargetRegisterClass *SrcRC;
 
   if (!TargetRegisterInfo::isVirtualRegister(SrcReg) ||
-      DstRC == &AMDGPU::M0RegRegClass)
+      DstRC == &AMDGPU::M0RegRegClass ||
+      MRI.getRegClass(SrcReg) == &AMDGPU::VReg_1RegClass)
     return false;
 
   SrcRC = TRI->getSubRegClass(MRI.getRegClass(SrcReg), SrcSubReg);
@@ -194,10 +196,10 @@ bool SIFixSGPRCopies::isVGPRToSGPRCopy(const MachineInstr &Copy,
 
 bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
   MachineRegisterInfo &MRI = MF.getRegInfo();
-  const SIRegisterInfo *TRI = static_cast<const SIRegisterInfo *>(
-      MF.getTarget().getRegisterInfo());
-  const SIInstrInfo *TII = static_cast<const SIInstrInfo *>(
-      MF.getTarget().getInstrInfo());
+  const SIRegisterInfo *TRI =
+      static_cast<const SIRegisterInfo *>(MF.getSubtarget().getRegisterInfo());
+  const SIInstrInfo *TII =
+      static_cast<const SIInstrInfo *>(MF.getSubtarget().getInstrInfo());
   for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
                                                   BI != BE; ++BI) {
 
@@ -236,14 +238,66 @@ bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
 
         // If a PHI node defines an SGPR and any of its operands are VGPRs,
         // then we need to move it to the VALU.
+        //
+        // Also, if a PHI node defines an SGPR and has all SGPR operands
+        // we must move it to the VALU, because the SGPR operands will
+        // all end up being assigned the same register, which means
+        // there is a potential for a conflict if different threads take
+        // different control flow paths.
+        //
+        // For Example:
+        //
+        // sgpr0 = def;
+        // ...
+        // sgpr1 = def;
+        // ...
+        // sgpr2 = PHI sgpr0, sgpr1
+        // use sgpr2;
+        //
+        // Will Become:
+        //
+        // sgpr2 = def;
+        // ...
+        // sgpr2 = def;
+        // ...
+        // use sgpr2
+        //
+        // FIXME: This is OK if the branching decision is made based on an
+        // SGPR value.
+        bool SGPRBranch = false;
+
+        // The one exception to this rule is when one of the operands
+        // is defined by a SI_BREAK, SI_IF_BREAK, or SI_ELSE_BREAK
+        // instruction.  In this case, there we know the program will
+        // never enter the second block (the loop) without entering
+        // the first block (where the condition is computed), so there
+        // is no chance for values to be over-written.
+
+        bool HasBreakDef = false;
         for (unsigned i = 1; i < MI.getNumOperands(); i+=2) {
           unsigned Reg = MI.getOperand(i).getReg();
           if (TRI->hasVGPRs(MRI.getRegClass(Reg))) {
             TII->moveToVALU(MI);
             break;
           }
+          MachineInstr *DefInstr = MRI.getUniqueVRegDef(Reg);
+          assert(DefInstr);
+          switch(DefInstr->getOpcode()) {
+
+          case AMDGPU::SI_BREAK:
+          case AMDGPU::SI_IF_BREAK:
+          case AMDGPU::SI_ELSE_BREAK:
+          // If we see a PHI instruction that defines an SGPR, then that PHI
+          // instruction has already been considered and should have
+          // a *_BREAK as an operand.
+          case AMDGPU::PHI:
+            HasBreakDef = true;
+            break;
+          }
         }
 
+        if (!SGPRBranch && !HasBreakDef)
+          TII->moveToVALU(MI);
         break;
       }
       case AMDGPU::REG_SEQUENCE: {
@@ -251,21 +305,22 @@ bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
             !hasVGPROperands(MI, TRI))
           continue;
 
-        DEBUG(dbgs() << "Fixing REG_SEQUENCE:\n");
-        DEBUG(MI.print(dbgs()));
+        DEBUG(dbgs() << "Fixing REG_SEQUENCE: " << MI);
 
         TII->moveToVALU(MI);
         break;
       }
       case AMDGPU::INSERT_SUBREG: {
-        const TargetRegisterClass *DstRC, *SrcRC;
+        const TargetRegisterClass *DstRC, *Src0RC, *Src1RC;
         DstRC = MRI.getRegClass(MI.getOperand(0).getReg());
-        SrcRC = MRI.getRegClass(MI.getOperand(1).getReg());
-        if (!TRI->isSGPRClass(DstRC) || !TRI->hasVGPRs(SrcRC))
-          break;
-        DEBUG(dbgs() << " Fixing INSERT_SUBREG:\n");
-        DEBUG(MI.print(dbgs()));
-        TII->moveToVALU(MI);
+        Src0RC = MRI.getRegClass(MI.getOperand(1).getReg());
+        Src1RC = MRI.getRegClass(MI.getOperand(2).getReg());
+        if (TRI->isSGPRClass(DstRC) &&
+            (TRI->hasVGPRs(Src0RC) || TRI->hasVGPRs(Src1RC))) {
+          DEBUG(dbgs() << " Fixing INSERT_SUBREG: " << MI);
+          TII->moveToVALU(MI);
+        }
+        break;
       }
       }
     }